Vacuum deposition is a common method for coating metals such as aluminum, copper, zinc, and tin onto various substrates of metal, glass and plastic. The metal is vaporized in a vessel commonly referred to as a "vaporization boat" by electric resistance heating. The vessel is connected to a source of electrical power to heat the vessel to a temperature which will cause the metal charge in contact with the boat to vaporize. Usually, the metal is vaporized in an evacuated chamber in which the product to be coated is placed. The product may be individually introduced into the evacuated chamber, or continuously fed through the chamber or, alternatively, may form part of the chamber itself. A wide variety of product is coated with metal using vapor deposition including ,e.g., television picture tubes, automobile headlights, toys and the like,
The metal charge is placed into a recessed cavity machined into the top surface of the vessel. Upon reaching the vaporization temperature of the metal the metal charge melts and quickly vaporizes. The charge flashes in a vigorous and abrupt manner and the process is repeated with a new charge of metal. The number of flashes which can be performed in a given time period controls product production. Accordingly, the number of flashes a vessel can sustain without failure is a critical performance characteristic of the process. Conversely, when failure occurs the parts being coated are scrapped or have to be redone which involves additional time and cost. To avoid this extra cost the vessel may be scrapped before its anticipated failure. Short life vaporization vessels increase production costs per part and reduce efficiency.